1. Field of the Invention
The invention relates to an indicator for determining and indicating the fat and moisture content of human skin, with a fat and moisture-sensitive substance applied to a substrate, which changes its color at least partially after being applied to the skin.
It is known that the skin of the face, in particular, is protected by a thin fat layer and emerging perspiration forming a coating for protection against acid. To this end, a particularly large number of sebaceous glands are present in the face, which produce fat in the form of sebaceous matter, with the sebaceous matter reaching the surface of the skin through outlet channels and providing a protection, particularly against the weather, in the form of a fatty film.
Larger sebaceous glands are located primarily in the socalled T-zone of the face, having the forehead as the crossbar and the nose down to the chin as the perpendicular portion of the T. Fatty, shiny zones can be seen there more frequently, while as a rule the cheek areas appear duller, because in that area the sebaceous glands are much smaller.
Of course, depending on the type of skin, the appearance of the skin varies or the individual facial regions are differently "greasy" because of a large sebaceous matter production, or "dry" because of a lack of water content of the uppermost skin layer. Sometimes it is hard to determine whether or not there is a lack of fat or moisture with skin which appears dry and chapped. In such a case there can always be a lack of moisture, i.e. in the fatty skin type as well as the dry skin type, while as a rule a lack of fat is only present in the dry skin type, so that in such a case a supply of moisture is required in most cases.
From a cosmetic point of view, the determination of the condition of the skin at many places and the selection of skin preparations which are suitable for the corresponding skin condition is important in that case in order to prevent damage or worsening of the skin condition.
In order to determine the skin condition it is known, for example from U.S. Pat. No. 4,532,937 to apply a thin, open-celled, microporous and hydrophobic film of a polymer material to the skin by means of an adhesive which is permeable to sebaceous matter and to leave it there for a while, in the course of which the pores of the film are filled with sebaceous matter and because of that become transparent, so that a first estimation of the sebaceous matter content is made possible in such a manner. However, the disadvantage of that method is that a reaction time of at least 30 minutes is required, and the method is not suitable for detailed studies and for the prolonged storage of the test results, because the sebaceous matter taken up in the pores has a tendency to spread rapidly over the entire film.